1. Field of the Invention
The present invention relates to mobile communication apparatus and, more particularly, to mobile communication apparatus of small size and low cost to be mounted in a vehicle, e.g., an automobile, car or truck also known more specifically as a road vehicle for affording radio communications with another such road vehicle.
2. Description of the Related Art
In existing digital radio communication apparatus to be mounted in a vehicle, two-way communication is conducted after determining the frequency (i.e., a “hand shake”) to be used for radio communication between a preceding vehicle and a succeeding, or following vehicle (i.e., “mobile-to-mobile communication”). To conduct two-way communication after a hand-shake, both vehicles are required to have a carrier oscillator which is capable of selecting a single frequency from among a plurality of frequencies.
However, a vehicle is required to have a set of two communication apparatuses, one for communicating with a preceding vehicle and the other for communicating with a succeeding vehicle. Therefore, it is necessary to provide such apparatuses in a smaller size and at a lower cost, relatively to what is currently available.
Moreover, it is also desired, to ensure safer travel, that it be possible to transmit information from a preceding vehicle to a succeeding vehicle more reliably, over greater distances, than is currently achieved in mobile-to-mobile communication between such preceding and succeeding vehicles.